A wide variety of transition metal ion-based bleaching catalysts have been studied, which enhance the stain-bleaching activity in detergent formulations by hydrogen peroxide, peracids and even oxygen. For example, dinuclear manganese catalysts based on triazacyclononane ligands are known to be particularly active catalysts in the bleaching of stains in laundry detergent products and in machine dishwash products and for treatment of cellulosic substrates present in e.g. wood-pulp or raw cotton (see for example EP 0 458 397 A2 (Unilever NV and Unilever plc) and WO 2006/125517 A1 (Unilever plc et al.).
Most attention has been directed to the use of manganese and iron ion-containing bleaching catalysts in laundry cleaning products, although catalysts have also been investigated in the context of automatic dishwash products. Iron complexes containing pentadentate ligands are efficient in stain bleaching without the use of hydrogen peroxide or peracid in the detergent formulations. For a more complete overview of the different classes of bleaching catalysts developed and studied, reference is made to R Hage and A Lienke (Angew. Chem., Int. Ed. Engl., 45, 206-222 (2006)).
Manganese salts and various manganese complexes are known to have a tendency to damage cellulose-containing (cellulosic) materials at certain temperatures, particularly in conjunction with hydrogen peroxide at high pH. The extent and damage profile depends, in part, on the catalyst employed, as is described, for example, in US 2001/0025695 A1 (Patt et al.). In this publication, there is a description of a far greater reduction in the viscosity of wood pulp cellulose when pulp was treated at high temperatures using a dinuclear manganese catalyst with 1,4,7-trimethyl-1,4,7-triazacyclononane (Me3TACN) than when a similar dinuclear manganese catalyst based on an ethylene-bridged ligand (1,2-bis(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)ethane) (Me4DTNE) was used.
In WO 01/64827 A1 (Unilever plc et al.), there is described the use of catalase enzymes or mimics thereof to decompose hydrogen peroxide that is initially present in a bleaching medium, so as to increase the amount of a transition metal ion-containing complex available for bleaching with oxygen. Separately, there is described in the same publication the timed release of a bleaching species or source thereof or an enzyme contained in the form of a granulate. Granulation aids described include a wide variety of materials including talc and clays. There is no teaching or suggestion in this publication that any of the granulation aids described, let alone talc or clays, could inactivate either a bleaching species or source thereof or an enzyme contained in the form of a granulate with such a granulation aid.
EP 0 710 713 A2 and EP 0 710 714 (both The Proctor & Gamble Company), describe the use of clay mineral compounds and crystalline layered silicates respectively for the purpose of reducing the problem of fabric damage, particularly of fabric colour fading, in order to address the dual challenge of formulating a product which maximises bleach soil soil/stain removal that minimises the occurrence of unwelcome fabric damage.
It is known that inorganic solid support materials, such as clays, can adsorb metal-ligand complexes and metal ions via cationic exchange mechanisms. An example of adsorption of manganese complexes containing N,N-bis(salicylidene)-ethylenediamine) (salen) ligands is described by J M Fraile et al. (J. Molec. Catal., 136, 47-57 (1998)). S Dick and A Weiss describe the adsorption of a dinuclear iron compound on clays (Clay Material., 33, 35-42 (1998)). Other metal complexes have also been reported to bind onto clays, for example a ruthenium complex to achieve oxidation catalysis (see R Ramaraj et al., J. Chem. Soc., Faraday Trans 1, 83, 1539-1551 (1987)). Moreover, as well as the possibility of removing metal ions using various clays, other inorganic solid support materials including carbon black are also known to adsorb metal complexes efficiently (for an example of carbon black in this context, see, for example, H Alt et al. (J. Catal., 28, 8-19 (1973)).
Whilst transition metal ion-containing bleaching catalyst have great utility in effecting bleaching of a variety of substrates, notably cellulosic substrates, the concomitant propensity to effect damage at certain combinations of pH, temperature and oxidising environment can be problematic. The present invention is intended to address this problem.